Install MozillaBuild, a package of additional build tools. (If you get a message saying this application did not install properly then you should see a windows dialog giving you the option to re-install with the 'correct settings'. After that all should be well.)

Open a shell window by running: c:\mozilla-build\start-msvcX.bat (where X is 8 for VS 2005, and 9 for VS 2008).

To build Thunderbird or SeaMonkey, you'll need more source code and some changes to your mozconfig file.

To build XULRunner, you will need changes to your mozconfig file as described in Building XULRunner.

On Windows, the above commands will create the mozilla-central directory in %USERPROFILE% which will likely be some subfolder of c:\Documents and Settings on XP or below. The space in this directory name, or in your user name if it contains one, will cause the configure script to break. To (possibly) fix this, cd to a dir without spaces before the "hg clone" command above.

The firefox executable can be found in objdir-ff-release/dist/bin/ (on Mac, objdir-ff-release/dist/Minefield.app/Contents/MacOS/).

How to build again later

In your mozilla-central directory, run these commands:

# Get the latest source
hg pull -r default
hg update

Then just re-run the "make -f client.mk" command above. make will only recompile files that changed, but it's still a long haul. An incremental build can be faster.